1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, such as a laser printer, a facsimile machine, or a copier, and more particularly, to a toner layer regulating member to form a uniform toner layer on a toner transfer unit and to electrically charge a toner by friction, and a developing device using the same.
2. Description of the Related Art
In general, an electrophotographic image forming apparatus forms a latent electrostatic image on a photosensitive surface and develops the latent electrostatic image into a visible toner image.
FIG. 1 is a schematic view of an electrophotographic image forming apparatus using a non-magnetic one-component toner. Referring to FIG. 1, the electrophotographic image forming apparatus includes a photosensitive body 1, a charging roller 2, an exposing portion 3, a toner transfer unit 5, and a transfer roller 9. Here, the photosensitive body 1 rotates in a predetermined direction. The charging roller 2 frictionally charges the surface of the photosensitive body 1 with a predetermined potential. The exposing portion 3 radiates light onto the photosensitive body 1 in accordance with a computer signal, to form a latent image thereon. The toner transfer unit 5 develops the exposing portion 3 with the latent image with a toner 8 stored in a toner container 4. The transfer roller 9 transfers the developed toner image to a paper 13. A supply roller 6 to attach the toner 8 to the toner transfer unit 5 and a toner layer regulating member 7 to form a toner layer with a predetermined thickness on the toner transfer unit 5 are installed outside the toner transfer unit 5.
In the above-described configuration, the charging roller 2 charges the photosensitive body 1 with electricity and then an electrostatic latent image is formed on the surface of the photosensitive body 1 by the exposing portion 3. The toner 8, which is non-magnetic, is supplied into the toner transfer unit 5 by the supply roller 6 and is made into a thin film having a uniform thickness by the toner layer regulating member 7. Here, the toner 8 is charged with high triboelectricity by the friction between the toner transfer unit 5 and the toner layer regulating member 7. The latent electrostatic image formed on the surface of the photosensitive body 1 is developed by the toner 8, which has passed through the toner layer regulating member 7, transferred to the paper 13 by the transfer roller 9, and fused by a fusing roller 12. The toner 8 remaining on the photosensitive body 1 is cleaned by a cleaner 10.
FIG. 2 shows a toner layer regulating member used in the above-described image forming apparatus, which is disclosed in U.S. Pat. No. 5,768,670. Referring to FIG. 2, a toner layer regulating member 7 uses a urethane rubber of rubber hardness 65 (according to a Wallace hardness meter) as an elastic layer 7b. Both sides of the elastic layer 7b are coated with a thermoplastic nylon resin to form an electrifying layer 7c. One side of the electrifying layer 7c is combined with a support member 7a, which is formed of phosphor bronze having a thickness of 150 μm. The electrifying layer 7c is made by dip-coating the elastic layer 7b with a thermoplastic nylon resin to electrify the toner by friction, and adhesion to the support member 7a. The electrifying layer 7c is adhered to the support member 7a by heat.
A method of manufacturing the toner layer regulating member will now be described. First, methyl alcohol 20% solution of AMIRUN CM4000 (produced by Toray Co., Ltd.) is applied to opposite surfaces of the urethane rubber by the dip coating method, and is air-dried at 80°. Here, the film thickness of the nylon is 20 μm, usually enabling film formation to be done uniformly. The rubber having the AMIRUN CM4000 film is cut into a predetermined size and set on a bed with a support member above and heated at 160° at a pressure of 0.5 kg/cm2 for 30 sec. Then, a thermoplastic resin is adhered on the surfaces of the rubber and the support member 7a. 
This method of manufacturing the conventional toner layer regulating member is very complicated. In particular, a thickness deviation occurs during the dip coating, and thus it is difficult to obtain a uniform toner layer. Also, weak adhesion to a base material such as the support member 7a causes the stripping of the layer from the surface of the base material. In this case, foreign substances are mixed during the dip coating, and thus it is difficult to form a uniform toner layer on the toner transfer unit 5.